1. Field of the Invention
The present general inventive concept relates to a hard disk drive apparatus, and more particularly, to a hard disk drive which can minimize a change in a magnetoresistance value of a read head due to electrostatic discharge.
2. Description of the Related Art
Hard disk drives (HDDs) include electronic parts and mechanical parts, as memory devices to record and reproduce data by converting digital electric pulses to a magnetic field that is more permanent. The HDDs are widely used as auxiliary memory devices of computer systems because of fast access time to a large amount of data.
A hard disk drive 100 as illustrated in FIG. 1 includes a disk 110 recording data, a spindle motor 120 rotating the disk 110, and a head stack assembly 130. An actuator arm 132 is provided at a side of the head stack assembly 130. A magnetic head 131 is mounted on the actuator arm 132 to record or reproduce data with respect to the disk 110. A voice coil motor (VCM) 133 rotating the actuator arm 132 is provided at the opposite side of the head stack assembly 130.
The hard disk drive 100 also includes various circuits related to the operational control of the magnetic head 131, the voice coil motor 133, and the spindle motor 120. These circuits are mostly provided on a printed circuit board (not shown) on a printed circuit board assembly 140 which is provided in a lower portion of a base 102 of the hard disk drive 100. A pre-amplifier (Pre-AMP) amplifying a signal read from the magnetic head 131 or a write current input to the magnetic head 131 is provided at a side of the head stack assembly 130 as one of the circuits in the printed circuit board assembly 140, and other circuits are provided on a portion other than the side of the head stack assembly 130.
A bracket 160 is provided on an upper surface of the base 102 to be connected to the printed circuit board. The bracket 160 and the pre-amplifier 140 are connected by a flexible printed circuit (FPC) 170. A plurality of metal wirings, that is, traces, are arranged on the FPC 170 as illustrated in FIG. 2. That is, The plurality of metal wirings are arranged to include a write trace 171 related to the write operation of the magnetic head 131, a read trace 172 related to the read operation of the magnetic head 131, a ground trace (GND trace) 173 performing a ground function, and a voice coil motor trace (VCM trace) 174 related to the operation of the voice coil motor 133. A connector or interface 150 is provided on the base 102 to connect the FPC 170 and an external device, such as a computer apparatus, through the bracket 160.
Recently, a compact hard disk drive is increasingly applied to electronic devices such as mobile phones or car navigator. Hard disk drives having a diameter of 2.5 inches or less are often referred to as the compact hard disk drive.
The miniaturization of the hard disk drive causes various technical difficulties. One of the technical difficulties is the deterioration of an electrostatic discharge (ESD) characteristic due to the decrease in a gap between the traces arranged on the FPC 170. The ESD can be easily found in everyday life and the ESD can be generated in parts such as the head stack assembly 130 or the FPC 170 of the hard disk drive, if it is not intended. It is widely known that, when a conductive body contacts an object having static electricity, the static electricity moves along a passage of the conductive body.
However, as illustrated in FIG. 1, when a hand of a user or an object capable of acting as a conductive body contacts the head stack assembly 130 or the FPC 170 before the hard disk drive is completely assembled, that is, before a cover 101 is capped, the static electricity remaining in the part has a flow. At this time, current flow instantly in the traces 171-174 of the FCB 170. Then, a magnetic field is formed around the traces 171-174 to electrically affect adjacent other trances 171-174.
In particular, it is important to consider the electric effect of the ground trace 173 or the voice coil motor trace 174 to the read trace 172. When current flows in the ground trace 173 or the voice coil trace 174 by the ESD due to the contact of a conductive body, an induced electromotive force is generated in the read trace 172 adjacent to a magnetic field formed by the traces 173 and 174. The induced electromotive force is proportional to the instant change rate of a magnetic field. Since the ESD is made very instantly, the induced electromotive force generated in the read trace 172 appears as a relatively high value. Thus, when the read head of the magnetic head 131 electrically connected to the read trace 172 is a magnetoresistive (MR) head, an excess current flows in the read head by the induced electromotive force generated in the read trace 172, so that a resistance value of the read head can deviate from an allowance. When the resistance value of the read head deviates from the allowance, the reading of the data by the read head cannot be normally made.
The generation of the excess current in the read trace 172 is more dominant in a compact hard disk drive in which the width of the FPC 170 is narrow. When the width of the FPC 170 decreases, the read trace 172 needs to be arranged closer to the ground trace 173 or the voice coil motor trace 174.
An ESD circuit which cuts off the flow of the excess current due to the ESD from the read trace 172 to the read head is provided in the pre-amplifier 140 which is connected to the FPC 170 at the side of the head stack assembly 130. However, since the size of the head stack assembly 130 needs to be decreased in the compact hard disk drive, the pre-amplifier 140 is difficult to be installed at the head stack assembly 130. That is, the pre-amplifier 140 needs to be installed at the position of the bracket 160 located on the upper surface of the base 102. The ESD circuit included in the pre-amplifier 140 cannot prevent the excess current due to the ESD transferred from the read trace 172 to the read head.